Auto focus (AF) is a great time saver that is found in one form or another on most cameras today. In most cases, it helps to improve the quality of the taken pictures. AF often uses a computer to run a miniature motor that focuses the lens of a camera. Focusing is the moving of the lens in and out until the sharpest possible image of the subject is projected onto a receiver, such as a Charged Coupled Device (CCD) or CMOS detector. Depending on the distance of the subject from the camera, the lens has to be a certain distance from the receiver to form a clear image.
A camera equipped with AF uses some type of measuring for computing in order to detect the distance of the subject from the camera and based on the measured distance, the lens is moved to a suitable position.
FIG. 1 illustrates a schematic AF system 100 of a camera. The system 100 comprises a lens 110 in a lens housing 120, which is arranged in a telescopic manner to be displaced inside a second housing 130. The lens housing 120 is arranged to be displaced by means of a stepper motor 140. The stepper motor 140 is controlled by means of a microprocessor 150, which receives signals from a measuring arrangement 160, measuring the distance to a subject to be photographed. The AF may be active or passive, both of which well known to a person skilled in the art.
In U.S. Patent Publication No. 20060107213, motion is used as an input to a program running on a mobile device. The mobile device may also require input from an alphanumeric or text input device. The motion can be used for items such as selection from a list, or navigation on a map. The motion can be sensed on image processing of the output of the camera, or can be directly determined using an accelerometer. The camera uses images as motion detection data.
According to GB 2416036, a camera is provided with accelerometer sensors which are arranged to detect either movement indicative of the camera being dropped or knocked out of a user's hands, in which case the motor control unit is instructed to automatically retract the camera's lens unit in the few tenths of a second before the camera hits the ground, or to detect substantial upward movement indicative of intended use when the camera is in a standby state with the lens unit retracted.
Traditional accelerometers comprise an acceleration detecting element, for instance a partly freely moving element with a mass that upon acceleration will move relative to other parts of the accelerometer. Detectors located adjacent the partly freely moving element will detect this movement and some processing unit can translate this to a measure of the acceleration. This is an often used design in micromechanical solutions, for instance in MEMS (Micro Electro Mechanical Systems) technology, where the accelerometer is built into a small integrated circuit and provides an electrical signal proportional to the acceleration. Accelerometers are sensitive to different frequency ranges. The accelerometers can be provided to give signals for accelerations in one, two or three directions or more. However, these “solid state” accelerometers are quite expensive and take up some area on a circuit board, which for some applications reduces the benefit of having them or increases the cost more than what customers are willing to pay for the product.